This document relates to devices based on optical resonators.
Optical resonators can be configured to exhibit high resonator quality factors for various applications, such as optical frequency references and optical filtering devices. A whispering gallery mode (WGM) resonator, for example, has a structure that confines light in a whispering gallery mode that is totally reflected within a closed circular optical path. Light in WGM resonators cannot exit the resonators by optical transmission and thus can be used to produce optical resonators with high optical quality factors that may be difficult to achieve with Febry-Perot resonators. Light in a WGM resonator “leaks” out of the exterior surface of the closed circular optical path of a WGM resonator via the evanescence field of the WG mode.